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NEET AIPMT SOLVED PAPER 1998

  • question_answer
                    The 21 cm radio wave emitted by hydrogen in interstellar space is due to the interaction called the hyperfine interaction in atomic hydrogen. The energy of the emitted wave is nearly:          

    A)                                 \[{{10}^{-17}}\,J\]           

    B)                 1 J          

    C)                            \[7\times {{10}^{-6}}\,J\]                             

    D)                 \[{{10}^{-24}}\,J\]

    Correct Answer: D

    Solution :

                    The energy of emitted photon                 \[E=\frac{hc}{\lambda }\]                 Given: \[\lambda =21\,cm=0.21\,cm\]                 \[\therefore E=\frac{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}{0.21}={{10}^{-24}}\,J\]


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